In many applications, particularly in the cooling system of internal combustion engines, hoses for various purposes are clamped to pipes or pipe nipples and are subjected to vibrations and to varying temperatures every time the engine is used. Consequently, during its life, a hose is subjected to loads and to repeated heating and cooling with resulting changes in stresses in the hose. This will tend to result in what is known as "compression set" or "plastic creep" in the hose. These terms are used to describe the tendency for the material of the hose to flow away from the clamp band leaving less material under the band so that the band will become too loose to seal the hose to the pipe. It is therefore desirable to provide a clamp which applies a substantially constant radial load on the hose as the hose changes shape under the band.
Prior art clamps, such as the clamp shown in U.S. Pat. No. 4,819,307, have addressed this problem by providing constant tension clamps having bands which are firstly tightened by rotating a worm screw in a housing, and then, once the band is snug around the hose, the screw is further tightened to load a spring to maintain a relatively constant clamping force should the hose reduce in size.
A further consideration in clamp design is to minimize the profile of the clamp so that the clamp is using up as little space as possible around the hose. Clearly the addition of a pre-loaded spring will tend to increase the profile and it is therefore desirable to include a spring arrangement which meets this design criterion. As seen in U.S. Pat. No. 4,819,307, the structure requires that the worm screw extend from both ends of a housing. Consequently, as the clamp is tightened the length of the structure about the housing remains constant and develops projections which are disadvantageous because they tend to snag on other engine components.
Accordingly, it is among the objects of the invention to provide an improved constant load clamp which reduces in profile as the clamp is tightened about a hose.